1. Field of the Invention
The present invention is directed to a table lift mechanism.
2. Description of the Prior Art
As is known, table lift mechanisms are commonly used on adjustable height work tables. Table lift mechanisms fulfill an ergonomic need for work surfaces to be height adjustable to accommodate workers of different heights and for the performance of different tasks.
In many embodiments, adjustable height work tables are supported either at each of their corners or cantilevered from supports at their rear two corners. The table height is adjusted through a table lift mechanism, which either extends and retracts the height of the supports to which the work surface is affixed or raises and lowers the work surface along fixed supports. Such table lift mechanisms have been formed by gear trains mounted to the supports. The table includes a rotatable drive shaft for engaging the gears mounted to the supports thereby to adjust the vertical position of the work surface. In one known embodiment, a table lift mechanism includes a rotatable drive shaft with a pinion gear for engaging a gear rack on the vertical support. In another known embodiment, a vertical linear drive comprises an elongated screw and a rotatable nut assembly, wherein a rotatable drive shaft engages the nut.
It is desirable to maintain a level work surface when its height is adjusted. This is achieved by incorporating a table lift mechanism at each support and simultaneously driving the gears within the lift mechanisms. A single rotatable drive shaft can be used to simultaneously actuate each lift mechanism by connecting cross shafts between gears within each table lift mechanism. Accordingly, one of the table lift mechanisms is driven by the rotatable drive shaft and torque is transferred to the table lift mechanisms at the other supports through the cross shafts, thereby simultaneously adjusting the height of each table lift mechanism.
In many of the known embodiments, a rotatable drive shaft directly engages a linear rack or a driven nut coupled to a screw. Consequently, these arrangements produce a high torque on the rotatable drive shaft to drive the linear rack or nut to which the rotatable drive shaft is directly coupled and further to drive the linear racks or nuts located on other supports to which it is coupled through a cross shaft. As a result, a direct coupling is prohibitive.
Further, in the known embodiments, the adjustment range of the table height is limited by the travel in the lifting mechanism. This range is typically 12 inches to 18 inches.
Further, existing table lift mechanisms do not allow for installation of one or more work surfaces on one set of supports, with both mounting systems having independent height adjustment.